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Author Topic: A question about a special kind of non-rubber tire/wheel system  (Read 1482 times)
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tallguy
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« on: September 09, 2017, 01:52:31 AM »

I didn't come up with this idea myself.  If I remember correctly, I saw this mentioned in an article about Waldo
Stakes . . . or maybe it was found on his website (several years ago).

For thrust-powered vehicles too fast to use rubber tires, it appears that a popular idea is to use solid wheels
made of aluminum.  I have no problem with that in principle, but the Bloodhound website pointed out that in the
foreseeable future, even this may not be suitable, as speeds may soon be about 1,000 mph.

It was mentioned, in reference to Waldo's car, that a different kind of wheel is being considered.  This would
have a rotating outer rim (possibly made of carbon fiber), and something like an air bearing between the rim
and the hub, which doesn't rotate.  I expect that the hub would be mounted on some kind of suspension, and
aerodynamic fairings would enclose the rim and hub, as well as the beam ("axle"?) that supports them.

I have been toying with this idea, and was wondering if anyone else (besides Waldo) has seriously
considered this.  I can imagine a hub made of aluminum, with something like water, some other liquid,
or perhaps some kind of gas, being fed, under pressure, through the hub, in order to provide a thin but
slippery cushion/layer between the hub and the rotating rim.

Perhaps the rim could be made of metal such as high-strength steel, as the rim could be fairly thin.  

I have thought about a project involving developing and testing of this kind of wheel, although I think it
would be fair to assume that this would be pretty expensive.  It's definitely beyond my financial ability
at the present time.  But researching to learn what's been done is relatively inexpensive.

I invite comments, questions, etc.   And I certainly am no expert about any of this.
« Last Edit: September 09, 2017, 01:59:33 AM by tallguy » Logged
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« Reply #1 on: September 09, 2017, 11:34:57 PM »

I'm sure I'm missing the point, since my knee-jerk reaction is that it merely increases the surface speed (tremendously) of the bearings- whatever they may be. huh
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« Reply #2 on: September 10, 2017, 05:46:53 AM »

     I read it as the water, or some other liquid, or gas, would be replacing the actual bearings.

     Way I see it is load plus high speed equals heat between moving parts and getting rid of the heat is key.  Using chemical mediums rather than conventional mechanical methods would mean some sort of flow system would have to be developed to carry away the heat unless some super chemicals can be developed.

                       Ed
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tallguy
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« Reply #3 on: September 10, 2017, 07:11:28 PM »

The fluid (liquid or gas) -- instead of balls or rollers -- would serve as the bearing(s).  Dissipating
heat would be a very important role, and this is why I have considered water, liquid nitrogen, and
other fluids.  Of course, liquid nitrogen might tend to make the rim and/or the hub dangerously
brittle if temperatures of these materials get too low.  Certainly, coefficient of thermal expansion
would have to be considered for each metal used.

The fluid flow rate required is likely to be pretty high; I imagine that perhaps about a liter per
second per wheel (or even substantially more) would not be out of the question.  And since it
would not be desired for the rim to rub directly against the hub at any time, I imagine that the
required pressure of the fluid, very carefully distributed, would be quite high also, with a large
portion of the flow entering the "bearing space" (between the hub and the rim) at or near the
bottom, where the hub tries to rest on the rim.  

I can envision the vehicle, on some temporary wheels (such as a trailer . . . or a "towing axle"),
being positioned and "aimed", and then lowered onto its racing wheels.  Then the bearing fluid starts
to flow, just before the actual run.  The bearing fluid would need to continue to flow until the
vehicle comes to a complete halt at the end of its run, perhaps 15 (or so) miles from the starting
location.  And since a good amount of force on the rim could come from aerodynamic drag, the
location of the main influx of fluid into the "bearing space" may have to be slightly -- or more than
slightly -- "forward" of BDC of the hub.  

Lots to think about.  Only if there is enough interest in this by racers could/would I get serious
about any kind of physical testing of this concept.  Perhaps some "air bearings" companies could
be of some assistance, based on their related existing knowledge and experience.  
« Last Edit: September 20, 2017, 07:20:51 PM by tallguy » Logged
WhizzbangK.C.
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« Reply #4 on: September 10, 2017, 09:04:04 PM »

The fluid (liquid or gas) -- instead of balls or rollers -- would serve as the bearing(s).  Dissipating
heat would be a very important role, and this is why I have considered water, liquid nitrogen, and
other fluids.  Of course, liquid nitrogen might tend to make the rim and/or the hub dangerously
brittle if temperatures of these materials get too low.  Certainly, coefficient of thermal expansion
would have to be considered for each metal used.

The fluid flow rate required is likely to be pretty high; I imagine that perhaps about a liter per
second per wheel (or even substantially more) would not be out of the question.  And since it
would not be desired for the rim to rub directly against the hub at any time, I imagine that the
required pressure of the fluid, very carefully distributed, would be quite high also, with a large
portion of the flow entering the "bearing space" (between the hub and the rim) at nor near the
bottom, where the hub tries to rest on the rim. 

I can envision the vehicle, on some temporary wheels (such as a trailer . . . or a "towing axle"),
being positioned and "aimed", and then lowered onto its racing rims.  Then the bearing fluid starts
to flow, just before the actual run.  The bearing fluid would need to continue to flow until the
vehicle comes to a complete halt at the end of its run, perhaps 15 (or so) miles from the starting
location.  And since a good amount of force on the rim could come from aerodynamic drag, the
location of the main influx of fluid into the "bearing space" may have to be slightly -- or more than
slightly -- "forward" of BDC of the hub. 

Lots to think about.  Only if there is enough interest in this by racers could/would I get serious
about any kind of physical testing of this concept.  Perhaps some "air bearings" companies could
be of some assistance, based on their related existing knowledge and experience. 

It would have to be a gas based system, since any liquid spewing out of the system would probably be seen as an environmental contaminant. I doubt that bleed air from a turbine engine would be sufficient in volume or pressure. Seems like the only possible way to get enough flow and pressure without excessive weight would involve combustion in some manner. Maybe solid fuel rockets firing into the rim/hub interstice, if you could find materials that could stand up to the temps.
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« Reply #5 on: September 11, 2017, 09:31:41 AM »

Perhaps a variation of this theme: http://www.popularmechanics.com/cars/a19747/goodyear-eagle-360-spherical-tires/
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Rex Schimmer
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« Reply #6 on: September 11, 2017, 11:59:47 AM »

It would appear that you are thinking about a system similar to what is called a "hydro-static" bearing system. These are used a lot in the machine tool industry to replace the roller or ball bearings in large spindles. The system normally consist of a typically bronze sleeve bearing that has pockets machine into its ID and oil, under pressure is pumped into the pockets which then supports the milling shaft on a film of oil. The system is very stiff, high load capabilities and very low friction. Hydro-static bearings are also used as linear bearings on very large machine tools again in place of roller or ball bearings. You need to recover the oil after it has travel through the bearing so it requires a fairly sophisticated sealing and recovery system. Some very high speed machine tools, milling shaft speeds exceeding 100,000 rpm, use air or a gas to further reduce friction and it does not require a recovery system but does require that the air or gas is extremely well filtered and also very dry.

It could certainly be done as a system for a very high speed vehicle but very expensive.

Rex
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tallguy
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« Reply #7 on: September 14, 2017, 08:27:27 PM »

Rex, this is what I have in mind, but not using any oil or other chemical that isn't environmentally friendly.
Water and liquid nitrogen appear to qualify in this regard.  I haven't done much thinking or research about
other possible fluids, but am willing to consider some that evaporate rather rapidly (like various types of
alcohol . . . perhaps this could help with cooling).  Flammability should be always be considered, as should
reactivity with other materials, such as the rim, hub, piping system(s), pumping system, fittings, storage
tank, regulator(s), etc.  It can certainly be complicated and challenging.  But what part of land speed
racing isn't complicated, challenging, and also expensive?
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« Reply #8 on: September 14, 2017, 11:57:21 PM »

The idea you have is exactly what the crankshaft main and connecting rods are doing. These journals are rotating around bearings and supported by the oil film between them under pressure. It is a closed recirculating system of course, so there is nothing being externally lost.

Turbocharger shafts rotate around journal bearings at 100,000+ RPM and don't wear much for the same reason - there is (almost) no metal to metal contact. As for the load forces, think of the forces that a connecting rod bearing experiences, especially in a big blown engine.

So the idea is a sound one that has been proven. It just takes someone to design a wheel to work the same as a journal bearing.

Don
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« Reply #9 on: September 15, 2017, 07:56:29 AM »

As described in the initial post, this concept seems to be based on a thin outer rim, or “tire” turning on a large diameter fluid bearing of some sort.  There are any number of reasons why this arrangement has not been used before and likely never will.

1)  How do you provide for lateral loads?
2)  Brakes would be nice.  How?
3)  There appears to be a misunderstanding of how fluid bearings (e.g. crankshaft) work.  The bearing is entirely dependent on the viscosity of the fluid, not supplied “oil pressure”.  Gases have very little viscosity and would need very closely fitted components as well as considerable flow volume and/or seals.  Liquids would require very high speed and precision sealing systems. 
4)  Large diameter high speed viscous bearing friction would likely be greater than small diameter rolling element bearings.
5)  How would a thin, and consequently flexible, “tire” maintain the required clearances and avoid radial deflections and circumferential  oscillations?
6)  Etc., etc. 
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tallguy
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« Reply #10 on: September 17, 2017, 01:13:55 AM »

Interested Observer, I was imagining the outer rim being approximately 1/2" thick, made of a relatively high-strength steel with good toughness.  Type 4340 steel comes to
mind.  It's used for gun barrels and helicopter main rotor shafts, because it is resistant to developing cracks. 

You asked good questions.  I'll try to answer them in order.

1.  The rim would have a "T-shaped" cross section, and have a central rib that "protrudes" inward toward the center.  That rib would be contained in a groove incorporated into the design of the hub, which would be comprised of 2 round pieces, each with a step, bolted together.  This is to allow the hub to be assembled around the one-piece rim.  Since the groove of the hub assembly would "contain" the rim, layers of fluid would need to keep the rim from moving very far either "outboard" or "inboard", direction-wise, on the hub.  The fluid would be dispensed through pathways (pretty much radial, perhaps) in the hub.  But I also believe that many pathways for the fluid would each have to be separately controlled, to keep the rim from rubbing ANYWHERE on the hub.  Not easy.  I envision the fluid layer being about .001" thick everywhere it exists, and being under
a pretty good amount of pressure until it escapes from the hub/rim assembly.

2.  Braking would mainly be provided by air brakes mounted in the fuselage (like on jet fighter aircraft), parachutes, and perhaps by a skid that rubs on the ground.  Breedlove's car had a skid.  The outer rim of each wheel could also be braked, but that's another big challenge.  None of this would be easy!

3.  I'm visualizing an extremely thin layer of fluid everywhere between the rim and the hub.  And of course, lots and lots of laboratory testing would be necessary before trying any of this on a vehicle.  The testing would have to be done while simulating the weight of the vehicle resting on the ground.  The testing would be done with various fluids
and all the various parameters would need to be developed, such as flow rate, pressure, etc.  I visualize a relatively non-polluting fluid, but have also considered carbon dioxide for this.  So far, I'm leaning toward plain old water.  Yeah, it's heavy.  But it also can soak up a lot of heat while phase-changing.  The vehicle might need to carry about a hundred gallons or more.  If brine is used, it could be quite cold at the start of the run.

4.  The main reason for this design is not to improve bearings.  It's to accommodate a lightweight rim that won't fly apart at high RPM. 

5.  All these things would have to be developed, with a lot of testing included.  Huge-bucks stuff!

6.  I second that etc., etc. motion.  It doesn't cost much to think/dream about future technology.  Stuff like that doesn't become reality until after someone has given it
enough thought, followed by a lot of effort and money.  I get it.  And yes, I'm not suggesting this will happen anytime soon.  Even if I were wealthy, I wouldn't try to develop
the technology unless somebody wanted it badly enough to pay for it.  And yes, the world does not absolutely NEED a 1,200 mph land speed car.  Agreed?
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